Shaped bodies of ceramics or glass may be manufactured from plastic, rather viscous masses which are first shaped, then dried and subsequently sintered.
The drying of green bodies manufactured from such masses is always problematic because during the drying process these bodies are subject to contraction which leads to mechanical stresses and consequently to the formation of cracks in the shaped body. The mechanical deformation of the green body is ultimately brought about by interfacial tensions originating from liquid laminae formed between the individual solid particles of the green body in the drying process. The absolute value of the mechanical stresses is determined by the concentration gradient of the liquid phase, which is formed in the drying process, and by the value of the interfacial-(surface)-tensions. Thus, to prevent the formation of cracks in the drying process it is generally required to conduct this process as slowly as possible, i.e., to aim at the smallest possible concentration gradients of the liquid phase.
In the art of ceramics the requirements to avoid dryingcracks are generally hard to fulfil. A slow drying process requires, for example, a substantial expenditure.